What is Causing Honey Bees to Disappear?

Honey Bees (Apis Mellifera)

After my recent blog on the environmental benefits of honey, readers have asked about global reports of bee declines. Among these reports is the case of the honey bee – one of many species of bees. This is different from the bumblebee (Bombus spp.), which you will probably have observed in your garden or eating pollen from wild flowers. In fact, there are hundreds of species of bumblebees. As for the honey bee, there are also many species, but the most common domesticated species used for honey production is Apis mellifera.

In 2006 people began to observe large numbers of honey bees vanishing from their hives. As you may know, less bees means less pollination of many of our crops. Without bee pollination, many foods can not be produced. For example, almonds would cease to exist if it weren’t for bees. Before I promise any answers, I should make clear there is no straightforward answer to what is causing honey bee deaths and their entire colonies to collapse. That’s why people have called this mysterious phenomenon “Colony Collapse Disorder”.  Here, I talk a little about what this means. 

Stacked White Boxes = 1 Bee Hive

My first real experience with honey bees occurred only recently. A few weeks ago, I introduced myself to Ben McGehee at the farmers market out of a curiosity regarding his work, and my love of honey. I asked if I could tag along on a day in the life of a beekeeper. When six-thirty am rolled around, and I was all suited up in my bee-gear, I went out with Ben, and his beekeeping student Mollie, to talk about bees and find out why colonies are collapsing.

Colony collapse is the loss of many adult worker bees from a single hive in a short time span. It does not necessarily affect all of the hives in one area, as Ben explained, but one day you may go out to find one or a few beehives absent of their adult bees. To give you an idea of what that means, a healthy hive can contain from 55, 000 – 70, 000 bees.  So, losing one hive is a devastating loss for beekeepers. As Ben, as well as researchers report, the cause, or causes, of colony collapse are not fully understood. 

So, what do we know?

Ben and Mollie Working at the Hives

Causes of colony collapse are thought to be multiple and interrelated. Pests and pathogens may be among the most important factors related to colony loss (Ratnieks and Carreck 2010).  One of these pests is the bee mite (Varroa destructor).  Mites alone however, cannot account for all the losses in bees.  In fact, the mites arrived to North America in the 80’s, but recently has it been suggested that they play a role in transmission of viruses that affect honey bees.  As Ben explained, the Varroa mite was first found on the honey bee in the USSR in the 60’s and appeared in the USA in the late 80’s. Although mites are believed to be important in the mystery of colony collapse, they are also problematic in general.  Most beekeepers have to treat for the mites no matter what, and this involves chemicals.  Ben has a few tips for natural ways of handling mites.  One is to dust the bees with powdered sugar. As the bees naturally groom themselves to rid themselves of sugar, they will hopefully clean off the mites too.  Natural ways of controlling for mites exist, but as Ben pointed out, they are less effective and involves a significant time investment for beekeepers.

Brood Comb Where the Queen Bee Lays Eggs

Mites and pathogens are probably not something most of us think about, however, there is one factor thought involved in colony collapse that will make us think twice…Pesticides. Pesticides, intended to rid fields and home gardens of insects other than bees, may also play a part in colony collapse. Honey bees forage during the day, collecting nectar and pollen from wild flowers or the flowers of agricultural crops. In doing so, they are subject to the harmful chemicals sprayed on crops or grasses. Honey bees are insects too, and just because they aren’t the target of pesticides doesn’t mean they aren’t harmed by them. If we continue to spray our fields with pesticides or support these practices by buying foods that are farmed with the use of pesticides, we may play more of a role in colony collapse than we would like to believe.  Although pesticides may not the primary cause of the collapse, it appears they are an important part of the puzzle. 

While out with Ben and Mollie, pesticides were mentioned to be a large concern for his 35 hives. Ben’s hives are placed in different agricultural fields, such as cotton and peanut, to help pollination (farmers hire him to complete this essential process). Spraying anywhere around these field can directly affect the foraging honey bees.

In sum, from what we know so far, a combination of agents are likely responsible for colony collapse.  These may include, pests and pathogens (mites, viruses), pesticide use, poor weather conditions that affect a bee’s ability to work, a lack of food, among other stressors. Although here I’ve described threats to domesticated honey bees, similar factors affect wild bumblebees (click here for a summary).  Unlike honey bees, bumblebees must make their own nests and suitable sites can become harder to find in fragmented habitats. Bee declines are indeed complicated, but what is good for the bees does not seem unreasonable. I know I prefer living near pesticide-free farms and landscapes that support flowers and nests for the bees.

Sources:

Ratnieks, F., & Carreck, N. (2010). Clarity on Honey Bee Collapse? Science, 327 (5962), 152-153 DOI: 10.1126/science.1185563

Goulson, D., Lye, G., & Darvill, B. (2008). Decline and Conservation of Bumble Bees Annual Review of Entomology, 53 (1), 191-208 DOI: 10.1146/annurev.ento.53.103106.093454